1. Field of the Invention
This invention relates to a process for foaming around the peripheral edge area of a cover, especially a glass cover, for a motor vehicle roof, the cover being placed on or in a foaming tool and the foam mass being fed into the foaming tool such that two foam mass fronts are formed which run towards one another in the peripheral direction and merge with one another or meet one another in a merging area. The invention furthermore relates to a cover for a motor vehicle roof in which two foam mass fronts which are formed during the peripheral foaming in the foaming tool merge with one another in the merging area.
2. Description of Related Art
FIGS. 1 and 2 schematically show a cover for a motor vehicle roof during or after peripheral foaming by means of a conventionally used process. The cover 10 is placed in a foaming tool in order to foam a carrier element 16, which is usually called the xe2x80x9cinside cover sheet,xe2x80x9d to the bottom of the cover 10 and to provide for a peripherally foamed edge area 18. In doing so, the foam mass, conventionally PUR, is added to the foaming tool from the sprue side 20, resulting in the formation of two foam mass fronts 22 in the peripheral direction of the cover 10, which fronts move towards one another in the peripheral direction of the cover and meet in an area 24 which is hereinafter called the merging area. Since ventilation takes place away from the peripheral area of the cover in the direction of the arrow 26, in the form of the front 22 shown, i.e., when the flow rate on the ventilation side 26 of the foaming tool is greater than on the opposite boundary edge, there is the danger that, in the merging area, on the boundary edge of the foam mass facing away from the ventilation side 26, air inclusions in the form of bubbles will occur. This area which is subject to bubble formation is labeled with reference number 30 in FIG. 2, which shows a section along the line IIxe2x80x94II in FIG. 1. These air inclusions cause a high scrap rate.
The primary object of this invention is to devise a process for foaming around the cover for a motor vehicle roof in which formation of bubbles due to air inclusions is prevented.
Furthermore, it is also an object to form a motor vehicle roof cover with an at least largely bubble-free foaming around the edge.
This object is achieved as claimed in the invention by a process in which the foaming tool is made such that, in the merging area, the foaming cross section on the side opposite the ventilation side of the foaming tool is reduced relative to the areas which border the merging area in order to prevent inclusion of gas bubbles in the merging area, and by a cover in which the cross section of the foam mass on the side opposite the ventilation side of the foaming tool is reduced relative to the areas which border the merging area. In this approach in accordance with the invention, it is advantageous that, especially by the corresponding configuration of the foaming tool, the probability of enclosure of gas bubbles in the foam mass in the merging area being pushed more towards the ventilation side of the foaming tool than in the areas adjoining the merging area.
Advantageous embodiments of the invention are explained in detail below by way of example with reference to the accompanying drawings.